A ceramic heater is a device for heating a semiconductor water in a process of manufacturing a semiconductor. FIG. 1 shows an example of such a ceramic heater 1.
The ceramic heater 1 is formed to include a ceramic substrate 2 that is a circular flat-panel member manufactured by using a ceramic material such as aluminum nitride (AlN) or aluminum oxide (Al2O3), a hollow shaft 3 that is attached to a bottom surface of the ceramic substrate 2 and has a hole H inside the hollow shaft 3, a heating wire 4 that is a metal wire of a three-dimensional (3D) coil type and arranged inside the ceramic substrate 2 to emit heat, a static electricity-generating electrode 5 that is a mesh-shaped metal member arranged inside the ceramic substrate 2, and generates static electricity to adsorb the semiconductor wafer, a first electricity-supplying member 6 that is a rod member that is arranged in the hole H of the hollow shaft 3 and supplies electricity to the heating wire 4, a first connecting member 8 for connecting the first electricity-supplying member 6 to the heating wire 4, a second electricity-supplying member 7 that is a rod member that is arranged in the hole H of the hollow shaft 3 and supplies electricity to the static electricity-generating electrode 5, and a second connecting member 9 for connecting the second electricity-supplying member 7 to the static electricity-generating electrode 5. Accordingly, the ceramic heater 1 heats the semiconductor wafer by using the heating wire 4, and adsorbs and fixes the semiconductor wafer by using static electricity generated by the static electricity-generating electrode 5.
As shown in FIG. 2, the ceramic heater 1 conventionally includes the heating wire 4 of a 3D coil type, and it may be difficult to maintain a shape of the 3D coil due to shrinkage deformation of the ceramic substrate 2 that may occur during sintering of the ceramic substrate 2.
Additionally, it may be difficult to maintain a heat density, required to design the ceramic heater 1, uniformly over the whole ceramic substrate 2 due to characteristics of a 3D coil, and deformation of a shape of the 3D coil which may occur during sintering.
Additionally, as shown in FIG. 3, since the heating wire 4 of a 3D coil type has a shape of a 3D coil which has a greater thickness W compared to a diameter D of a cross section, generated heat spreads out in all directions. Accordingly, compared to a heating wire of a two-dimensional flat-surface type which generates the same amount of heat as that generated by the heating wire 4, an amount of heat generated in an upper direction, that is, in a direction necessary to heat the semiconductor wafer may be reduced.
Additionally, since the heating wire 4 of the 3D type has a shape of a 3D coil, a worker may not easily arrange the heating wire inside the ceramic substrate 2. Thus, the ceramic substrate 2 may have to be manufactured by using a powdered raw material.
In order to solve such problems of the heating wire 4 of the 3D coil type, a heating wire of a 2D flat surface type (not illustrated) which is manufactured in the form of a thin sheet by using metal paste was used.
However, although the heating wire in the shape of a thin sheet may implement a uniform heat density, since a method of manufacturing the same may be limited to etching, paste printing, or the like, the heating wire in the shape of a thin sheet may be manufactured to have only a small thickness. Thus, a physical connection of the heating wire to the first connecting member 8 may be worsened, and anticorrosion and durability of the heating wire may be worsened.
Additionally, when viewed from over the ceramic substrate 2, the heating wire in the form of a sheet has a larger top flat surface than the heating wire 4 of the 3D coil type. Accordingly, since the heating wire in the form of a sheet may have a smaller heat density per unit area compared to a heating wire that has the same cross section and the same length as the heating wire in the form of a sheet, the heating wire in the form of a sheet may have a slow temperature ramp-up speed.
Accordingly, there is a need to develop a heating wire for compensating for respective problems of the heating wire 4 of a 3D coil type and the heating wire in the form of a sheet.